Use of fusible metals in drilling wells



.. 23, I941. 4 N. JOHNSTOYIV 2,257,633v

USE OF FUSIBLE METALS IN DRILLING WELLS Filed Jan. 10, 1939 NORRIS JOHNSTON INVEN TOR A TTORNEY Patented Dec, g,

use or FUSmLE METALS m nae Norris..lohnston, Alhambra, -Calif., assignor to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Application January 10, 1939, Serial No. 250,174 7 claims. (or. ice-2m) The present application is a continuation in part of my copending application Serial No. 210,842, filed'May. 31, 1938, and'entitled Method of coring to preserve fluid content. I

The copending application discloses a method for taking cores during the drilling of a well which consists substantially in introducing a fusible metal into the well, raising the temperature of the circulating fluid to melt the metal and form a metallic pool in the bottom of the hole, taking a corefrom beneath the metallic pool, raising the core barrel to allow metal to flow into its lower end, solidifying the metal by lowering the temperature of the circulating fluid, and withdrawing the core barrel with its lower end plugged and sealed with solidified metal.

I have discovered that the general principle of the copending application may be utilized in other mannersand for other purposes than those already disclosed.

For example, a fusible metal may be used for the recovery of small objects, such as bit rollers or roller bit pins, which maybe lost in the hole and which are diflicult to recover or drill up because they roll on the bottom'of the hole. By solidifying a mass of molten metal around them,

in the manner hereinafter described, such ob-- jects are maintained in a fixed position and may b milled out, or ahole may be drilledthrough the relatively soft metal block and the entire block, including the lost object, fished out of the well. Because the metal has, as a rule, a higher slewin -gravity than steel, the lost object will usually float to the surface of the molten metal and be imprisoned in the upper part of the block when the metalis solidified.

inside the casing drilled out; and Fig. 4 illustrates the use of a packer for displacing the molten metal from inside the casing before it is chilled. v

Referring first toFig. 1, i0 is an earth bore passing through one or more impervious strata A, B, and C and through a porous stratum D, for instance a layer of water bearing gravel, and entering a lower impervious stratum E.

The first step is to raise-the casing until its lower end is above the top of stratum D and preferably above the level to which it is desired to seal the wall of the well. A sufiicient quantity of a metal of the proper melting point, as will later be described, to form a pool of the required depth, is then introduced into the well an any convenient manner, as by dropping in bars or blocks of the metal. The melting point of the metal, for this specific purpose, must be such that it will be solid at the normal temperature at the bottom of anothervaluable use for the fusible metals is I coldfluid over its surface, and the metal inside the casing, ifany, is drilled out.

This procedure is diagrammatically illustrated ir the attached drawing, in which Fig. 1 illustrates the formation of the pool of molten metal at the bottom of a hole; Fig. 2 shows the casing lowered into position before the metal solidifies; Fig. 3 shows the metal solidified and the metal the well--which mustfirst be accurately determined-and that it can be melted at a temperature not far above the bottom-hole temperature.

The well casing H and drill pip'elZ being new at moreor less the positions shown in Fig. 1, the temperature of the circulating mud is raised above the melting point of the metal, as for instance by steam pipes immersed in the mud stream' at the surface of the ground or by injecting direct steam into the mud stream. Circulation of the relatively hot mud is then continued until the temperature at the bottom of the hole is such as to melt the metal and to cause it to form the pool indicated at id in Fig. 1. A

When this condition is reached, circulation is interrupted temporarily and the casing s lowered until it rests on the bottom of th hole, as shown in Fig. 2. The circulation, which initially was down. the drill pipe and upwardly either inside or outside the inner casing string ll, nowreturns inside the casing. The drill pipe is retained in its original position, with its open end above the surface of the metal. After the lowering of the casing, circulation is resumed with mud at. a

manner illustrated in Fig. 4, by displacing most M i :01: the fmolten metafl from inside the basins by I meltin point or sa 160 would b ndie I 1 r f the; at a packer OIE plug; f fill this operation ated: would be melted with; some; i e; pooigoi molten metal is romeo as in: Fig. apidity by raising the: temperature 101'; the bin and the easing is weredias: iii-fig; 2. until it ciiilatins fluid? about *185 :i ?ahr.- and;would be l7 almost but not; quite touches the bottom or :the: 1 solldined within is re s able time by lower ns hole. The packer or plug indicatedat ii: in Fl he temperature the ci clflatin fluilfl; tO- Sall '4 is their run to the bottom or; the hole; displac Fans-.1 Alloys ranging in melting pointtrom; the molten metal Efrem inside; theorising and 50? to 225 Palm, in ,5", steps. :would; probably zeroing 1 it upwardly; outside casing. iThB cover; the entire range: or miitiogrs; likely to he,

' kermust be provided withloencounteredw'e i :=i

rculation opening or the: cold :ifluid. and the lloys havin idefl ite me ns' 111k? i 1 E lower one must b of sushi form and: material cient; mechanical strength to resis unb lanced 1 was it not be ozfen in place: by any? Solidi?- hydraulic pressures are available over, a wide f I fled metal r'err'i'a'in'ing 1 temperature; range; g'li'he compoundingoiiuslble 7 operation results in a considerable saving of the metals 8, W8 1, known lrt and: the manner; of I rather expensive rrusible metal, but requires considerable :rriorei tir'n hen the method first :de-

in detah; in general etals :of' this class are. alloys of, bismuth; lead. tin-. cadmium; and; anti Q yn i d ifi 1 1 1 5 131% e 733F990? tar-ed iormahions I nor: to: any censiclerable dis;- tense :into even; an i open formation such: as a ates Ebearing gravel It does, i however; :iorm; a

, t j i ap b e; of e n 1 thems t neonditioe y contact; with; a heated aqueous hold such, as: ri ling mud and m re s s i e laiaime ei ev mus sears applying; hiei metal. ithoiush less risorouis cleaning is required: than: the 151 8 of cathe: nor nz ,.;temperaiture: wi h n said? well, and;

need: at any; desired later: time; semi cutting mpora y m idiisi s sa d me a y s mulat n the; casing; provide or course: that: the strin 7 has not frozen; i e tormatioh i itseli'i Tore- 7 1 I move the metallic seal it is necessary merely to: ous fluid previously; cooled in a; temperature below; i

reheat the well to a temperature above the meltsaid melting point. ing point of the metal, which will cause it to 2. In the drilling 01* Wel s by od inflow down the space between the casing and the volving the circulation of fluid within the well, wall and permit its removal from the bottom or the method of sealing the lower end of the well the well. Thus in case a number or thin water asing to the wall of the well which comprises: bearing strata are encountered it is possible to introducing into said well a fusible metal havshut ofl repeatedly and in a minimum of time ing a melting point above the normal temperature for each operation. at the bottom of the well; maintaining said metal For some uses it is preferable to employ a V in the state of a molten pool at the bottom 01 the metal which is molten at the normal bottom hole well by circulating within the well an aqueous temperature. In such case themetal is solidifluid heated to a temperature above said melting fled temporarily by circulating a relatively cold point; setting said casing with its lower and subfluid instead of being melted by hot circulation. stantially touching the bottom of the well; dis- It will also be obvious that the metal may be placing at least part of the molten metal from introduced in molten form, in the hot circulawithin said, casing into the annular space betion or by loweringa superheated and insulated tween said casing and the wall of the well, and capsule containing it to the bottom of the well. solidifying said metal by circulating within the While the fusible metals are more costly than well a fluid having a temperature below said cement, they may in some cases be substituted melting point. to advantage for permanent "cementlng or casw 3. In the drilling oi wells by a method involving to the wall 0! the well. The advantage in ing the circulation of fluid within the well, the the use 01' metal lies in itshigh specific gravity, steps comprising: introducing into said well a which tends to make it produce a sealing ring or fusible metal; placing said metal in a liquid equal height on all sides, thus completely sur- 1 state at a point where a solid casting is desired; rounding the pipe and avoiding the channeling 6 and changing saidmetal from the liquid state sometimes experienced in the use of cement. to the solid state by circulating in heat inter- In case the cementing operation is to be perchange relation therewith a fluid having a temformed at a level above the well bottom, it will peraturc below the melting point of said metal. be obvious to use a packer to retain the metal 4. In the drilling of wells by a method involvat the proper level. .m ing the circulation of mud fluid within the well, The choice of alloy melting point rests on the the steps comprising: introducing into said well temperatures existing in the particular well to a fusible'! metal; placing said metal in a liquid which the method is to be applied. For examstat a a point where a s d astin is d sir d; pie, it the predetermined temperature at the botand 81118 Said metal fr m h quid s ate to tom of the well is 150 Fahn. a-metal having a the solid state by circulating in heat interchange relation therewith mud fluid having a temperature below the melting point of said metal.

5, In the drilling of wells by a method involving the circulation of mud fluid within the well, the steps comprising: introducing into said well a fusible metal having a melting point below the normal temperature within said well, and temporarily solidifying said metal by circulating in heat interchange relation therewith mud fluid previously cooled to a temperature below said 10 melting point.

6. In the drilling of wells by a method involving the circulation of mud fluid within the well; the steps comprising: introducing into said well a fusible metal having a melting point above the normal temperature at the bottom of the well; bringing said metal to the state of a molten pool on the well bottom by circulating within the well mud fluid heated to a temperature above aaeaees 20 said meltingpoint; and solidifying said metal by circulating within the well mud fluid having a temperature below said melting point.

7. In the drilling of wells by ,a method involving the circulation of mud fluid within the well, the method of sealing the lower end of the well casing to the wall of the well which comprises: introducing into said well a fusible metal having a melting point above the normal temperature at the bottom of the well; maintaining said metal in the state of a molten pool at the bottom of the well by circulating within the well mud fluid heated to a temperature above said melting point; setting said casing with its lower end substantially touching the bottom of the well; displacing at least part of the molten metal from within said casing into the annular space be- 

